: : Actually the force between the two particles varies as 1/r**2 according to Newton and substantiated by every test and observation since his time, except for relativistic effects. Thus two particles next to each other would experience increasing attractive force as they moved closer rather than cancelling out.

Richard, It is this idea that the gravitational force varies, that I don't buy into. I believe we will eventually come to understand that gravity as a function of mass, is constant.